Anemia is defined as a reduction in the hemoglobin concentration of the blood, usually associated with a reduction of total circulating red cell mass. Regardless of the cause, anemia decreases the oxygen-carrying capacity of the blood, and when severe enough, causes clinical symptoms and signs.
Clinically, anemia is characterized by pallor of the skin and mucus membranes, and by manifestations of hypoxia, most commonly weakness, fatigue, lethargy, or dizziness. Myocardial hypoxia may produce hyperdynamic circulation with an increase in heart rate and stroke volume. Ejection type flow murmurs may develop, and if the anemia is severe enough, cardiac failure may ensue.
Anemias are generally classified in one of two ways: either by etiological classification (based on the cause) or by morphologic classification (based on changes in shape and size). Etiological classification is more commonly employed. The invention covered by this application is primarily concerned with anemias implicating the immune system.
Autoimmune hemolytic anemia (AIHA) caused hemolysis occurs due to autoantibody production by the body against its own red blood cell (RBC) membrane. These anemias are divided into two classifications based on the reactivity of the antibodies involved: warm (antibody reacts at 37.degree. C.) or cold (4.degree. C.). [Hoffbrand, A. V. in Essential Hematology, 3rd. ed., Blackwell Scientific Publications, 1993, p. 87]. Certain immune disorders such as collagen vascular diseases, chronic inflammatory bowel disease, chronic lymphocytic leukemia, or lymphomas are associated with an increased incidence of AIHA [Andreoli, T. in Essentials of Medicine, W. B. Saunders, 1986, p. 349].
Warm AIHA is characterized by RBC coated with IgG alone, IgG with complement, or complement alone. RBCs are taken up by macrophages, especially in the spleen. Cells become more spherical to maintain volume and are prematurely destroyed, typically in the spleen, resulting in an splenomegaly and microcytosis. Warm AIHA occurs alone, or in association with other diseases, and can arise as a result of methyl dopa therapy. When it is associated with idiopathic thrombocytopenic purpura, it is known as Evan's Syndrome. Warm AIHA has an insidious onset and a chronic course. Treatments include corticosteroids (prednisolone), splenectomy, removing underlying cause (methyl dopa). Immunosuppressants may be tried after other measures fail, but are not always of great value; azathioprine, cyclophosphamide, chlorambucil, and cyclosporin A (CsA) have been tried. Blood transfusions with blood that is the least compatible and lacking antigens (if auto-Ab is known) may be needed. [Hoffbrand, A. V. in Essential Hematology; 3rd. ed., Blackwell Scientific Publications, 1993, p. 87 and Chandrasoma, P. in Concise Pathology, 1st. ed, Appleton and Lange, 1991, p. 398].
With cold AIHA, the antibody involved is usually IgM and binds to RBCs best at 4.degree. C. The antibodies are usually directed against the `I` antigen on the RBC, and attach to the RBCs mainly in the peripheral circulation where the blood temperature is cooled. Agglutination of RBCs by the antibody often causes peripheral circulation abnormalities. Idiopathic cold AIHA is a rare cause of hemolysis that occurs mainly in older patients. Patients may have a chronic hemolytic anemia aggravated by the cold. Patients present with cold-induced hemolysis or Raynaud's phenomenon present with mild jaundice and may develop acrocyanosis (purplish skin color) at tips of nose, ears, fingers, and toes due to the agglutination of RBC in the small vessels. Splenomegaly may be present:. Secondary cases are seen after Mycoplasma pneumonia or infectious mononucleosis. Treatment consists of keeping patient warm, and treating underlying cause, if present. Alkylating agents may be useful; splenectomy does not usually help, unless massive splenomegaly is present. Steroids are not helpful. [Hoffbrand, A. V. in Essential Hematology, 3rd. ed., Blackwell Scientific Publications, 1993, p. 89; and Chandrasoma, P. in Concise Pathology, 1st. ed, Appleton and Lange, 1991, p. 398].
Alloimmune hemolytic anemia occurs when the antibody of one individual reacts with RBC of another. Alloimmune hemolytic anemia typically occurs following transfusion of ABO incompatible blood and rhesus disease of the newborn. It also can occur following allogenic transplantation. [Hoffbrand, A. V. in Essential Hematology, 3rd. ed., Blackwell Scientific Publications, 1993, p. 90].
The administration of certain drugs can cause transient drug induced anemia. This can occur by three mechanisms: 1 ) antibody directed agianst a drug-red cell membrane complex (e.g., penicillin or cephalothin); 2) deposition of complement via drug-protein (antigen)-antibody complex onto the red cell surface (e.g., quinidine or chloropropamide) or 3) an autoimmune hemolytic anmeia in which the role of the drug is mysterious (e.g., methyl dopa). In each case, the anemia disappears only after the drug is discontinued (however, with methyl dopa, the antibodies may persist for many months). [Hoffbrand, A. V. in Essential Hematology, 3rd. ed., Blackwell Scientific Publications, 1993, p. 90-1].
Aplastic anemia is defined as pancytopenia (anemia, leucopenia, and thrombocytopenia) resulting from aplasia of the bone marrow. It is classified into primary types: a congenital form (Fanconi anemia) and an acquired form with no obvious precipitating cause (idiopathic). Secondary causes may result from a variety of industrial, iatrogenic and infectious causes. The underlying cause appears to be a substantial reduction in the number of hemopoietic pluripotential stem cells and a defect in the remaining stem cells or an immune reaction against them making them unable to divide and differentiate sufficiently to populate the bone marrow. [Hoffbrand, A. V. in Essential Hematology, 3rd. ed., Blackwell Scientific Publications, 1993, p. 121]. Suppresser T-cells as well as immunoglobulins that inhibit erythropopieten or block differentiation of hemopoietic stem cells in vitro have been demonstrated in some cases. [Andreoli, T. in Essentials of Medicine, W. B. Saunders, 1986, p. 349].
Fanconi type aplastic anemia is a recessively inherited condition that is associated with growth retardation and congenital defects of the skeleton, of the renal tract, skin, and often mental retardation. The typical age of presentation is 5-10 years old. Treatment; is usually with androgens or bone marrow transplantation. [Hoffbrand, A. V. in Essential Hematology, 3rd. ed., Blackwell Scientific Publications, 1993, p. 122-3].
Idiopathic acquired aplastic anemia is thought to be an autoimmune condition in which the patient's T-lymphocytes suppress the hemopoietic stem cells. Clinical response is often seen with anti-lymphocyte globulin (ALG), corticosteroids, and CsA. In some instances, a defect of the marrow stem cells which limits their proliferative capacity seems likely. [Hoffbrand, A. V. in Essential Hematology, 3rd. ed., Blackwell Scientific Publications, 1993, p. 123]. Clinical features include infections (mouth, throat, and generalized bruising, bleeding gums, epistaxes, and menorhagia. This condition is often life threatening. The lymph nodes, liver, and spleen are not enlarged. [Hoffbrand, A. V. in Essential Hematology, 3rd. ed., Blackwell Scientific Publications, 1993, p. 123-4].
ALG is of benefit in about 50-60% of acquired cases, and is thought act via the elimination of suppresser killer T-cells. Serum sickness, fever, rashes, hypotension, or hypertension, however, are side effects. CsA therapy given with ALG and high doses of corticosteroids appears to be of additional benefit. Approximately, 50-60% of patients respond to ALG and up to 80% respond to combined ALG, steroids, and CsA. CsA alone, provides improvement in an occasional patient. [Hoffbrand, A. V. in Essential Hematology, 3rd. ed., Blackwell Scientific Publications, 1993, p. 126].
Rapamycin is a macrocyclic triene antibiotic produced by Streptomyces hygroscopicus, which was found to have antifungal activity, particularly against Candida albicans, both in vitro and in vitro [C. Vezina et al., J. Antibiot. 28, 721 (1975); S. N. Sehgal et al., J. Antibiot. 28, 727 (1975); H. A. Baker et al., J. Antibiot. 31,539 (1978); U.S. Pat. No. 3,929,992; and U.S. Pat. No. 3,993,749].
Rapamycin alone (U.S. Pat. No. 4,885,171) or in combination with picibanil (U.S. Pat. No. 4,401,653) has been shown to have antitumor activity. R. Martel et al. [Can. J. Physiol. Pharmacol. 55, 48 (1977)] disclosed that rapamycin is effective in the experimental allergic encephalomyelitis model, a model for multiple sclerosis; in the adjuvant arthritis model, a model for rheumatoid arthritis; and effectively inhibited the formation of IgE-like antibodies.
The immunosuppressive effects of rapamycin have been disclosed in FASEB 3, 341 (1989). Cyclosporin A and FK-506, other macrocyclic molecules, also have been shown to be effective as immunosuppressive agents, therefore useful in preventing transplant rejection [FASEB 3, 3411 (1989); FASEB 3, 5256 (1989); R. Y. Calne et al., Lancet 1183 (1978); and U.S. Pat. No. 5,100,899].
Rapamycin has also been shown to be useful in preventing or treating systemic lupus erythematosus [U.S. Pat. No. 5,078,999], pulmonary inflammation [U.S. Pat. No. 5,080,899], insulin dependent diabetes mellitus [Fifth Int. Conf. Inflamm. Res. Assoc. 121 (Abstract), (1990)], smooth muscle cell proliferation and intimal thickening following vascular injury [Morris, R. J. Heart Lung Transplant 11 (pt. 2): 197 (1992)], adult T-cell leukemia/lymphoma [European Patent Application 525,960 A1], and ocular inflammation [European Patent Application 532,862 A1].